1. Field of the Invention
The present invention relates generally to a multihop relay wireless communication system, and more particularly, to a method for constructing a frame of a Relay Station (RS) to support a relay service in the multihop relay wireless communication system, and an apparatus for supporting the method.
2. Description of the Related Art
A wireless communication system is able to allocate uplink/downlink resources using a Time Division Duplex (TDD) scheme and a Frequency Division Duplex (FDD) scheme.
Using the FDD scheme, the wireless communication system separates uplink and downlink using frequency resources.
Using the TDD scheme, the wireless communication system splits uplink and downlink using time resources over the same frequency band.
For the TDD scheme, the wireless communication system splits a frame to a transmit (Tx) interval and a receive (Rx) interval using the time resource as shown in FIG. 1.
FIG. 1 illustrates a typical frame structure of an Institute of Electrical and Electronics Engineers (IEEE) 802.16 system.
A j-th frame 100 of FIG. 1 includes a DownLink (DL) subframe 101 and an UpLink (UL) subframe 103 which are split using the time resources.
A Base Station (BS) constructs a BS frame 120 over the j-th frame 100, which includes the DL subframe 101 for sending a DL signal to a Mobile Station (MS) and the UL subframe 103 for receiving a UL signal from the MS. A Transmit/Receive Transition Gap (TTG) 105 is a time guard region that lies between the DL subframe 101 and the UL subframe 103 of the BS frame 120. A Receive/Transmit Transition Gap (RTG) 107 is a time guard region that lies between the j-th frame 100 and a (j+1)-th frame 140.
The MS constructs an MS frame 130 over the j-th frame 100, which includes the DL subframe 101 for receiving the DL signal from the BS and the UL subframe 103 for sending the UL signal to the BS. The MS receives the DL signal from the BS after a DL delay (e.g., DownLink one way Delay (DLD)) caused by the radio channel. The MS sends the UL signal by considering an UpLink one-way Delay (ULD) so that the BS can receive the UL signal over the UL subframe 103 of the BS frame 120.
For the delay of the radio channel, a Subscriber Station Receive/Transmit Transition Gap (SSRTG) 113 is the time guard region that lies between the DL subframe 101 and the UL subframe 103 of the MS frame 130. A Subscriber Station Transmit/Receive Transition Gap (SSTTG) 115 is the time guard region that lies between the j-th frame 100 and the (j+1)-th frame 140.
As discussed above, the BS and the MS construct the BS frame 120 and the MS frame 130 including the time guard region for the operation switch between the DL subframe 101 and the UL subframe 103 respectively. In doing so, the TTG 105 of the BS frame 120 is designed to have the same value as the summation of the DLD, the SSRTG 113, and the ULD. The RTG 107 of the BS frame 120 is designed to be equal to the value acquired by subtracting the DLD and the ULD from the SSTTG 115 in length.
Recently, to reconfigure the network more rapidly in response to changes in the communication environment and to utilize the wireless network more efficiently, research on communication methods using a Relay Station (RS) are being conducted in the wireless communication system. Since an RS relays signals between a BS and an MS, the wireless communication system requires not only a link between the BS and the MS but also a link between the BS and the RS and a link between the RS and the MS. Therefore, what is needed is a new communication method and a new frame structure for the communication methods using an RS in the wireless communication system.